Wax emulsions have been used in composite wallboard (e.g., gypsum wallboard) for many years. For example, wax emulsions sold under the trade name AQUALITE® by Henry Company, and several wax emulsion formulations are disclosed in the prior art, such as U.S. Pat. No. 5,437,722, hereby incorporated by reference in its entirety.
Gypsum is employed in a gypsum panel or board product known as wallboard which is widely used as a structural building panel. Gypsum products are produced by mixing anhydrous calcium sulphate or calcium sulphate hemihydrate with water and allowing the mixture to hydrate or set as calcium sulphate dihydrate which is relatively hard. Gypsum wallboard comprises a panel-like core of set gypsum sandwiched between a pair of paper facers, or liners, which form the exposed outer surfaces of the wallboard. Fiberglass facers have also been used. In many applications wallboard is exposed to water. A problem with set gypsum is that it absorbs water, and such absorption reduces the strength of the wallboard.
U.S. Pat. No. 3,935,021, hereby incorporated by reference in its entirety, describes a gypsum wallboard in which polyvinyl alcohol and a wax-asphalt emulsion are incorporated in the gypsum core. In manufacturing wall board there are several properties needed to achieve acceptable products, including low edge swell and water absorption as well as strong internal bond strength and good flexural stiffness and flexural strength.